Fate and mechanism of clearance of PSAP, a schistosome antigen, in schistosomiasis.

The clearance and the factors modulating clearance of PSAP, a glycoprotein excretory-secretory antigen of Schistosoma mansoni, were determined in control and infected mice. After i.v. injection, PSAP was removed rapidly from the circulation of both infected and control mice. The half-life in control mice was about 2.5 min compared to 60 min for the proteoglycan schistosome gut antigen, GASP. Injection of PSAP-containing immune complexes into control mice or of PSAP into infected mice resulted in a prolongation of clearance. In infected mice, the delay in clearance correlated with the amount of anti-PSAP. Marked inhibition of clearance was induced by coinjection of asialofetuin with PSAP, indicating a galactose-mediated clearance mechanism. Furthermore, the clearance of model complexes was delayed to a greater degree after co-injection of asialofetuin than with aggregated gamma-globulin, suggesting that complexes were primarily removed by the galactose receptor. The delay in clearance of antigens may result in immune complex deposition in abnormal locations.